How to make Vim open existing buffers with NERDTree

Question

I recently discovered NERDTree and Command-T but when I open files that has already been opened I get the really annoying "VIM - ATTENTION Swap file already exists" popup and I click abort and then I search through the buffer instead(!).

So my question is whether there is a setting to switch on so that it always opens the buffer for the file if it already exists.

Answer 1

Found the solution:

:set hidden

It should be noted that the Janus MacVim Distro doesn't turn this feature on by default.